There is continuing effort in electronic industry to achieve higher circuit density in electronic devices. To archive higher degree of integration, new and improved lithographic tools and techniques have been developed which in turn demand new photoresists that could enhance the resolution of lithographic patterns. Aqueous base developable photoresist compositions which are formed through crosslinking have been disclosed in Reck et al., SPIE regional Technical Conference on Photopolymers, Ellenville, N.Y., 63 (1988) and in U.S. Pat. No. 5,034,304 and 5,204,225 to Feely. Such formulations were characterized by polymers having an aromatic moeity, like poly(hydroxystyrene) or novolak, which are susceptible to electrophilic aromatic substitution, and a crosslinking agent which can form a carbonium ion upon treatment with acid and a photoacid generator.
U.S. Pat. No. 4,810,601 to Allen et al. is concerned with formation of negative tone resist patterns by crosslinking an aromatic compound with monomeric or polymeric source of carbonium ions. Thus, diacetoxymethyl benzene and trisacetoxymesitylene were used with triphenylsulfonium hexafluoroantimonate to crosslink a poly(hydroxystyrene) matrix.
U.S. Pat. No. 5,296,332 to Sachdev and Japanese patents 2-15270 and 1-293339 to Kokai describe aqueous base deviopable resist composition comprising of a phenolic resin like poly(hydroxystyrene) or Novolak, a crossinkable agent which can form carbonium ion upon treatment with acid, and a photoacid generator.